CAS IfSet for S3 KV Store

[Euraxluo]

I believe the original reason for closing this issue is no longer valid after S3 added native ETag-based conditional writes.

Closed discussion

[arielshaqed]

Hi @Euraxluo !

The new feature will probably make it possible to resolve the correctness issue in the old issue. The other issue is performance. i wrote a bit more about it on 7967